Functional Neurological Symptom Disorder (FND), as defined in DSM-5, is a psychiatric condition characterized by unexplained neurological symptoms affecting voluntary motor or sensory functions. Although it appears to mimic genuine neurological or medical illnesses, clinical and laboratory evaluations reveal no underlying organic cause. The symptoms are typically involuntary and are not consciously produced by the individual.

Historically, this disorder was explained through the concept of “conversion,” in which internal psychological conflicts were thought to manifest as physical symptoms. In modern psychiatry, this approach has been replaced by integrative biopsychosocial models, although psychological factors remain highly relevant in diagnosis and treatment processes.

DSM-5 Diagnostic Criteria for Functional Neurological Symptom Disorder

According to DSM-5, the following criteria must be met for the diagnosis:

• One or more symptoms affecting voluntary motor or sensory function (e.g., paralysis, speech disturbances, numbness, seizures).
• Clinical findings demonstrate incompatibility between the symptom and recognized neurological or medical conditions.
• The symptom causes clinically significant distress or impairment in social, occupational or other important areas of functioning.
• The symptom is not better explained by another medical or mental disorder.
• There is clinical evidence that the symptom is not consciously produced or feigned for secondary gain.

A key diagnostic criterion is the involuntary nature of the symptoms. Unlike malingering or factitious disorder, the symptoms are not intentionally fabricated.

Symptoms of Functional Neurological Symptom Disorder

Symptoms vary widely and are commonly categorized as follows:

• Motor Symptoms: Paralysis, muscle weakness, restricted movement, tremors, gait disturbances.
• Sensory Symptoms: Numbness, tingling, loss of vision or hearing, reduced tactile sensation.
• Seizure-like Symptoms: Events resembling epilepsy but without epileptic activity on EEG.
• Speech and Swallowing Disturbances: Aphonia (loss of voice), dysphonia (hoarseness), dysphagia (difficulty swallowing).
• Coordination Problems: Ataxia, balance disturbances.

These symptoms often develop suddenly, sometimes following stressful or traumatic events, though not always with an identifiable trigger.

Etiology of Functional Neurological Symptom Disorder

The etiology cannot be reduced to a single factor. Instead, it is considered to emerge from the interaction of genetic vulnerability, neurobiological sensitivity and psychosocial stressors. Commonly proposed explanatory models include:

• Psychodynamic Theories: Symptoms are viewed as unconscious transformations of psychological conflicts into physical manifestations, potentially serving as a means of escape or secondary gain.
• Behavioral Theories: Physical symptoms may be reinforced by external attention and support from the environment.
• Neurobiological Findings: Recent neuroimaging studies indicate that conversion symptoms may be associated with functional disruptions in brain networks, particularly inhibition or dysfunction in motor-related regions.

Traumatic life experiences, childhood abuse and the presence of psychiatric comorbidities such as anxiety and depression are significant contributing risk factors.

Risk Factors for Functional Neurological Symptom Disorder

Major risk factors include:

• Childhood trauma (especially sexual, physical or emotional abuse)
• Female gender (higher prevalence among women)
• Low socioeconomic status
• Low educational level
• History of medical illness or chronic pain
• Comorbid psychiatric disorders (notably anxiety, depression and dissociative disorders)

Diagnosis

Diagnosis requires a multidisciplinary approach. A thorough medical and psychiatric history, physical examination and appropriate investigations are necessary. The hallmark is that symptoms lack medical explanation and are inconsistent with clinical findings.

Typical diagnostic clues include:

• Symptoms that do not follow anatomical patterns
• Inconsistencies between observed behavior and reported impairment (e.g., claiming inability to walk yet demonstrating sudden ability in emergency situations)
• Variable neurological examination findings

Neuroimaging (MRI, EEG) and laboratory tests are used primarily to exclude organic causes. Psychiatric evaluation is essential to assess comorbidities such as somatic symptom disorder or depression.

Treatment of Functional Neurological Symptom Disorder

Treatment requires a comprehensive approach that addresses both the symptoms and underlying psychosocial factors.

1. Psychoeducation and Diagnostic Explanation

The first step involves carefully explaining the diagnosis. Patients should be informed that symptoms are real but related to functional brain changes, not malingering. This reduces stigma and enhances treatment adherence.

2. Psychotherapy

• Cognitive Behavioral Therapy (CBT): Focuses on symptom understanding, stress management and functional restoration.
• Trauma-focused Therapy: Particularly effective in patients with trauma histories.
• Psychodynamic Therapy: Aims to address unconscious conflicts underlying the symptoms.

3. Physiotherapy and Rehabilitation

For motor symptoms, physical therapy can improve functionality and build confidence in movement.

4. Treatment of Comorbid Psychiatric Disorders

Anxiety and depression should be addressed with appropriate pharmacological treatment (e.g., antidepressants) alongside psychotherapy.

5. Long-term Follow-up and Support

Ongoing monitoring, psychoeducation sessions and community-based support may be necessary.

Impact on Daily Life

Functional Neurological Symptom Disorder can significantly impair quality of life. The resulting disability may lead to occupational impairment, strained social relationships and dependence on others for daily activities.

Some patients become long-term disabled, while others remain frequent users of health services as “mystery” patients. This creates a substantial burden on healthcare systems and can damage doctor-patient relationships through unnecessary tests and treatments.

Because symptoms do not produce visible changes in physical appearance, they may be underestimated by others, contributing to stigma, social isolation and feelings of loneliness in affected individuals.